Measurements of the dielectric constants of materials at different frequencies are used in many different measurement schemes. For example, capacitance measurements at low frequencies are used to distinguish between oil and water. In the oil and gas sectors, for example, dielectric scanners may measure these constants at frequencies up to 1-2 GHz to determine water volume and rock properties. In addition, Fourier transform infrared (“FTIR”) measurements in the infrared region may be used to determine mineralogy of core samples.
Other measurements demanding sample preparation, such as those utilizing helium pycnometry are unable to provide accurate results in the case of unconventional oil and gas reservoirs that possess low permeability. Nuclear magnetic resonance (NMR) based measurements of pore volume may be used, but are often limited by the small pores in unconventional samples that cause fast relaxation times in the NMR signal that are difficult to accurately measure. Commercial measurements today are generally based on utilizing crushed samples but these techniques both add uncertainty due to the crushing process and also are destructive measurements may demand extensive sample preparation.
Other techniques for identifying the mineralogy of core samples include diffuse reflective infrared Fourier transform spectroscopy (DRIFTS). However, due to similarity of FTIR spectrum of smectite and illite samples, DRIFTS is unable to accurately distinguish between these notable constituents of shale beds. Similar issues in accurately determining the concentrations of illite and smectite have been observed in measurements taken with X-ray diffraction (XRD).